Passive Optical Networks (e.g. Indoor Passive Optical Networks) are becoming prevalent in part because service providers want to deliver high bandwidth communication capabilities to customers. Passive optical networks are a desirable choice for delivering high-speed communication data because they may not employ active electronic devices, such as amplifiers, repeaters, and work group switches, between a central office, data center, or equipment room and a subscriber termination or user device. The absence of active electronic devices may decrease network complexity and/or cost and may increase network reliability.
Many companies have a maximum allowed downtime per year. That downtime can be anywhere from a few minutes to a few days. When the allowable downtime is exceeded, the costs can be enormous. The allowable downtime is usually planned downtime and does not allow for downtime as a result of failure. To help alleviate this problem, systems designers create redundancy so that there is a back-up path and electronics to keep the system going in the event of failure. The head-end electronic equipment may have the ability to sense a path failure and to automatically activate the redundant path.
FIG. 1 illustrates an example network 100 deploying passive fiber optic lines. As shown, the network 100 can include a central office 101 that connects a number of end subscribers (also called end users herein) in a network. For example, the network 100 may connect head end electronics at the central office 101 to one or more wall plates 150 at subscriber locations 105. Near end electronics may be connected to the wall plates 150 using one or more optical patch cords. The central office 101 can additionally connect to a larger network such as the Internet (not shown) and/or a public switched telephone network (PSTN).
One or more of the end subscriber locations 105 may be disposed in a multi-dwelling unit (MDU) 110. The MDU 110 can include a fiber distribution hub (FDHs) 120 that may accept a primary feeder cable FP including one or more incoming fibers and a back-up feeder cable FB including the same number of incoming fibers. The FDH 120 may split or optically couple the incoming fibers of the primary feeder cable FP to individual subscriber distribution fibers SD that may be associated with end user locations 105. The FDH 120 also may split or optically couple the incoming fibers of the back-up feeder cable FB to the individual subscriber distribution fibers SD.
In general, primary and back-up lines cooperate to define redundant paths to an example subscriber location 105. As shown in FIG. 1, a first subscriber distribution fiber SD1 is routed along a first path P1 from the FDH 120 to an example wall plate 150 at an example subscriber location 105. A second subscriber distribution fiber SD2 is routed along a second path P2 from the FDH 120 to the example wall plate 150 at the subscriber location 105. In the passive optical network 100, the primary optical path P1 and the back-up path P2 each use a dedicated port 152, 154 on the wall plate 150.
A near end electronic device 140 connects to the primary port 152 using an optical patch cord PC to receive the optical signals carried over the first subscriber distribution line SD2. The near end electronic device 140 may include a media converter 145 that converts the optical signals to electrical signals. For example, the converter 145 may output the electrical signals (e.g., along four twisted pair wires 148) to electrical contacts (e.g., spring contacts of an RJ-jack). When a failure occurs, the optical patch cord PC connecting the wall plate 150 to the near end electronic device 140 has to be switched manually from the primary port 152 to the back-up port 154 to allow the electronic device 140 to receive optical signals from the second subscriber distribution line SD1.
Such manual switching increases the downtime when a failure occurs. Further, such manual switching may introduce dirt or other contaminants into the optical path, which also may increase downtime to clean and verify the path. Also, such manual switching can cause delays associated with negotiation between electronic components of the system. In view of the above, other types of redundancy systems are desirable.